The present invention relates generally to metallized films, and in particular to a metallized film having structured layers, as well as a method for the production of such films and their uses.
Certain metallized films, for example safety films, are known in the prior art. For example, WO 99/13157 discloses safety films for securities and methods for their production. Such a safety film for incorporation or application in or on securities includes a translucent supporting film and a metallic coating applied thereon with metal-free regions that are clearly visible particularly with transmitted light. For the production of these metallized films, the supporting film is prepared, then a printing ink with high pigment content is printed on the supporting film, the printing ink is then dried to form a porous, raised color coating. After formation of a thin metallic masking layer on the thus imprinted supporting film, the color coating and the masking layer which is lying over it or resepctively penetrating into the color coating are removed by washing with a liquid, possibly combined with mechanical action, and finally the supporting film is dried and optionally cut to shape. The metallic masking layer thus remains on the supporting film in those areas originally not covered by the printing ink and may have a thickness of 0.01 μm to 1 μm according to the publication.
Furthermore, EP 0 330 733 A1 discloses a safety element in the form of a thread of a translucent plastic film, which has an opaque coating extending across the element and including recesses in the form of characters or patterns to be incorporated and which contains at least in the areas congruent to the recesses coloring and/or luminescent substances, by which the characters and/or patterns are distinguished under suitable light conditions from the safety document and from the opaque coating in contrasting colored form.
In another prior art publication, DE 36 87 250 T2, a method of making metallizing dielectric carriers is disclosed, wherein a layer of metallic chrome is vapor-deposited on a dimensionally stable polyimide substrate under vacuum conditions and afterwards a copper layer is galvanically applied on this chromium layer. In order to produce a desired pattern on the conductive copper tracks, the copper layer is etched and then a layer of gold or tin or a solder is applied on these conductive tracks.
DE 36 10 379 A1 discloses a method of making a film provided on at least one of its surfaces with a metal layer interrupted at preselected spots. In this method, the metal layer is applied in the preselected spots onto a poorly sticking substrate and mechanically cleared away from the preselected spots. In this way, the poorly sticking substrate can be so distributed across the entire surface of the film that the desired pattern is realized. Regardless of this pattern, the entire surface is then metallized, so that the metallization can be accomplished relatively inexpensively. Since the layer of metal is only loosely applied on the poorly sticking surface, it can be removed from the surface relatively easily by mechanical means.
Other metallized films and methods for their production are known, for example, from EP 0.107,983 A1, EP 0.479,058 A1, EP 0.600.374 A1, DE 198 34 348 A1, DE 198 15 175 A1, DE 198 12 932 A1, DE 196 43 823 A1, DE 197 18 177 A1, DE 197 29 891 A1, DE 198 22 075 A1, DE 198 18 968 A1, U.S. Pat. No. 4,242,378, U.S. Pat. No. 4,685,997 and U.S. Pat. No. 4,863,808. To avoid mere repetitions of the respective contents, their full disclosure is incorporated herein by reference, in particular with respect to the structures, layer thicknesses and materials of the metallized films as well as the process steps for the production of patterns with the metallic layer.
While for particular applications, such as, e.g., safety films for securities, some applications of metallized films in principle desire to keep the metallic layer as thin as possible, so that it is spread as little as possible, other applications require thicker and nevertheless cleanly structured or formed metallic layers with fine pattern, which cannot be made in a satisfactory way by conventional methods, such as, e.g,. for conductive tracks or printed boards, particularly for antennas, as found, e.g. in cell phones.
It would therefore be desirable and advantageous to provide safety films for securities with improved metallized films to obviate prior art shortcomings and to create a metallized film and a method for its production.